The present proposal is a fundamental research program to study systematically diffusional and interfacial phenomena between the phases existing in amalgamation process. Data on diffusion properties in the multiphase-multicomponent system in question will be obtained for three metals (Ag, Hg, and Sn) that are the principal components of dental amalgams. The phases to be studied include Ag3Sn, gamma 1 (Ag2Hg3) and gamma 2 (HgSn8). Among the results, especially significant were the results of the diffusion studies in the gamma/gamma 1 diffusion couples. It is believed that the following two mechanisms could be responsible for the gamma 1 yields beta 1 phase transformation in dental amalgams: (1) the interfacial reaction between gamma 1 and Ag3Sn and (2) the diffusion in and out of dental amalgam constituents at the surface of the gamma 1 polyhedra due to the surface diffusion.